1. Field of the Invention
The present invention relates to a module to enable better utilization of fibers within multi-fiber trunk cables. More particularly, the present invention relates to an adapter module to facilitate a connection between a plurality of fiber optic transceivers and a plurality of multi-fiber trunk cables.
2. Description of the Related Art
As illustrated in FIG. 1, a known fiber optic transceiver 21 has a twelve fiber, multiple-fiber push-on/pull-off (MPO) receptacle 23 that accepts an MPO connector plug 47 shown in FIG. 3. More detail concerning the MPO receptacle 23, the MPO connector plug 47 and an associated multi-fiber trunk cable can be found in the Assignee's prior U.S. Pat. No. 7,416,347, which is herein incorporated by reference. The multiple-fiber push-on/pull-off (MPO) connector is generally known in the art. Such connectors relate to IEC-61754-7 and EIA/TIA 604-5 (FOCIS 5) standards. The internal structures and functioning of the fiber optic transceiver 21 are also known in the art and not needed for an understanding of the present invention. Therefore, reference can be had to the prior art for a better understanding of the fiber optic transceiver 21.
FIG. 2 depicts the fiber mating face within the MPO receptacle 23 of FIG. 1. The MPO mating face has four transmit channels (Tx) and four receive channels (Rx). Typically, the first four channels 1-4 are used for transmission of data and the last four channels 9-12 are used for the reception of data. The middle four channels 5-8 are unused, perhaps reserved for the future use of fiber optic transceivers with expanded abilities.
As seen in FIG. 2, the MPO receptacle 23 contains an MPO mating face 24 with twelve fiber ends 1-12 arranged in a linear row between two alignment features 25, such as alignment pins or alignment holes. An MPO receptacle containing an MPO mating face will be referred to as an MPO port. FIG. 2 is depicting the alignment features 25 as alignment pins, and as such the fiber optic transceiver 21 has a male MPO port designed to receive a female MPO connector plug without pins of an incoming fiber optic trunk cable or patch cord.
FIG. 3 illustrates a connection between a first fiber optic transceiver 31 on a first printed circuit board 30 and a second fiber optic transceiver 33 on a second printed circuit board 32, both having a same construction as the fiber optic transceiver 21 of FIG. 1. As illustrated, a multi-fiber trunk cable 35, having twelve optical fibers therein, is used to connect the first fiber optic transceiver 31 to the second fiber optic transceiver 33. A first female MPO connector plug 37 at a first end of the trunk cable 35 is provided for mating with a first male MPO port 39 of the first fiber optic transceiver 31. A second female MPO connector plug 41 at a second end of the trunk cable 35 is provided for mating with a second male MPO port 43 of the second fiber optic transceiver 33. In practice, the trunk cable 35 may extend over a long distance within a building environment (e.g., from a networking closet on a ground floor to a networking closet on a 20th floor) or within a campus environment (e.g., from a computer lab building to a dormitory networking closet). The trunk cable 35's length could perhaps range from several meters up to one thousand meters.
Often, a keying arrangement is provided at the first and second MPO ports 39 and 43 and the first and second MPO connector plugs 37 and 41. In a known embodiment of the keying arrangement, the first and second MPO ports 39 and 43 include a slot 45 and the first and second MPO connector plugs 37 and 41 include a protruding rib 47, such that the first and second MPO connector plugs 37 and 41 may only be connected to the first and second MPO ports 39 and 43 in one orientation (i.e., in the “key up” orientation, as depicted).
FIG. 4 depicts the interconnections between the first and second fiber optic transceivers 31 and 33, as well as the interconnections between third and fourth fiber optic transceivers 49 and 51 and between fifth and sixth fiber optic transceivers 53 and 55, in accordance with the prior art. As can be seen in FIG. 4, four of the twelve fibers within the first trunk cable 35 connecting the first fiber optic transceiver 31 to the second fiber optic transceiver 33 are unused. Also, four of the twelve fibers within a second trunk cable connecting the third fiber optic transceiver 49 to the fourth fiber optic transceiver 51 are unused. Also, four of the twelve fibers within a third trunk cable connecting the fifth fiber optic transceiver 53 to the sixth fiber optic transceiver 55 are unused.